This invention relates to a system for coupling independently operable vehicle controllers, and more particularly to a system for linking pilot and co-pilot control inceptors in an aircraft. Coupling these sidesticks according to the invention enables them to experience substantially identical motion.
During the flight of an aircraft, actions of the pilot and co-pilot are conveyed to an aircraft flight control system which interprets them and executes them by moving the various control surfaces on the aircraft. More specifically, the pilot-and co-pilot maneuver sidestick controllers (also known by those skilled in the art as xe2x80x9ccontrol inceptorsxe2x80x9d) in the cockpit that are directly or indirectly linked to the various aircraft control surfaces. In a mechanical flight control system, the sidesticks can be linked to the control surfaces via, cables and linkages. Such a system is disclosed in U.S. Pat. No. 5,456,428 to Hegg issued Oct. 10, 1995, the contents of which are hereby incorporated by reference in their entirety. In an electronically controlled aircraft, commonly known as a xe2x80x9cfly-by-wirexe2x80x9d aircraft, sidestick motion is transformed into electrical signals which are typically transmitted to the control surfaces via servomotors, actuators or similar devices. An example of a fly-by-wire control system is disclosed in U.S. Patent No. 4,472,780 to Chenoweth et al. issued Sep. 18, 1984, the contents of which are hereby incorporated by reference in their entirety.
Controlling an aircraft using electronic rather than mechanical flight controls allows the commands that are executed in the cockpit to be augmented by additional inputs from flight control computers, and thereby allows for more efficient aircraft operation.
Presently available civil fly-by-wire aircraft control the aircraft using independently operable pilot and co-pilot sidesticks. There are significant operational and safety benefits of connecting these sidesticks to cause each to move in a pattern that is substantially identical to that of the other. One benefit of linking the sidesticks is to increase the level of safety by providing increased situational awareness for the pilots. That is, the pilot and co-pilot will each be able to closely monitor what the other is doing. Thus, in the event that one of them improperly directs the aircraft (i.e. due to a sudden illness) the other will immediately recognize the error and be able to correct it. Linking the two sidesticks is also beneficial for pilot training.
Sidesticks and other control inceptors are typically designed to operate at very light force gradients and small displacements. These factors place very stringent requirements on the quality of the coupling between the sidesticks. Inability to meet these requirements will adversely effect overall pilot feel. Arrangements for coupling pilot and co-pilot sidesticks are known. However, these known systems have significant limitations. For example, a mechanically controlled system may be limited by:
Hysteresis, friction: inherent to all mechanical transmissions and have a detrimental effect on system performance. However, in sidesticks, they represent a larger contribution with respect to basic operating feel forces and therefore present an increased design challenge because such small forces and displacements are involved. The significant friction forces that can exist between the moving parts often make it difficult for the pilots to precisely move the sidestick and achieve smooth control of the aircraft. Moreover, backlash, which results when the connections that join moving parts are too loose, can also jeopardize the pilot""s ability to maintain precise control of the aircraft;
Jam potential: also inherent to all mechanical transmissions and has a detrimental effect on the safety of the aircraft.
Wear: also inherent to all mechanical transmissions. Wear leads to performance degradation over time and adversely impacts the ability to maintain the system.
Installation: Mechanical transmissions have tight tolerances to ensure adequate performance. This typically requires careful and lengthy manufacturing, installation, and rigging.
Weight, inertia: Weight is a critical parameter in aircraft design. For a given distance between the sidesticks, the mechanical coupling will tend to be comparatively heavier than other forms of coupling. The resulting inertia will adversely affect pilot feel and the resulting aircraft handling qualities.
Electronically controlled coupling systems are also somewhat limited. First, electrical servomotors have significant authority, torque, and rate requirements because they are designed to provide maximum feel forces and to accommodate pilot/co-pilot contention, which occurs when the two pilots are simultaneously applying opposite force input commands to their sidesticks. In such a case, the servomotors must generate resistance forces on each of the two sidesticks. These resistance forces simulate sidesticks that typically would be rigidly coupled up to an acceptable level of force fight, and hence provide awareness that contention is taking place. These forces must be fairly large and need to be generated rapidly in order to provide adequate notice to the pilots.
Moreover, servo driven control systems are typically subject to active failure modes. For example, runaway (drift of the sidestick when the motor malfunctions), hardover (maximum drift of the sidestick when a motor fails), and uncommanded motion, can all produce catastrophic results. Servo driven control systems therefore, require high integrity to minimize the occurrence of such failure modes, and to safely and quickly cope with them. These systems also require complex electronic force fight management, and tight loop closure (i.e. high gain, bandwidth, sampling rate, feedback accuracy) in order to provide the required force level and coupling stiffness as well as the quick reaction time required for fault identification and system reconfiguration in the case of a failure. The need to satisfy these requirements results in very complex solutions and generates significant costs.
It would be desirable to be able to provide a device that allows the motion of each sidestick controller to efficiently and accurately follow that of the other.
It would also be desirable to provide a coupling system that avoids active failure modes.
It would also be desirable to provide a sidestick coupling device which is easy to install.
It would also be desirable to provide a sidestick coupling device which minimizes jamming, wear, hysteresis friction and mass inertia.
In accordance with the present invention, there is provided a system for coupling multiple control inceptors, each of which directly controls the motion of a vehicle. The system includes multiple controllers, each of which independently directs the motion of the vehicle, and a coupling assembly associated with at least two of the controllers. The coupling assembly varies a fluid distribution to cause the controllers to have substantially identical motion.
In a particularly preferred embodiment, the coupling assembly may connect both the pitch and roll degrees of freedom of two sidestick controllers. For one degree of freedom this embodiment includes two chambers placed on opposite sides of each of the controllers. A fluid displacer in each of the chambers is linked to its associated controller. The two chambers associated with each sidestick are connected to the two corresponding chambers that are associated with the other sidestick via two conduits. Each pair of chambers and the conduit that connects them are sealed and substantially filled with fluid. Fluid is transported between the connected chambers in response to motion of the fluid displacers. The same configuration and operating principle applies to the second sidestick axis.
The present invention may be constructed to control motion about one, two or more than two axes of motion. It may also be used to couple more than two controllers. dr
The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:
FIG. 1 is a schematic representation of coupling of two single degree of freedom controllers according to one embodiment of the invention;
FIG. 2 is a schematic illustration of a sidestick controller that may be used with the present invention, placed in the coordinate system used to describe the invention;
FIG. 3 is a detailed view of an exemplary embodiment of the invention for dual axis sidestick controllers;
FIG. 4 is a side view of a coupling assembly according to the preferred embodiment of the present invention;
FIG. 5 is a schematic representation of an embodiment of the invention that provides multiple conduits for a single degree of freedom;
FIG. 6 is a schematic representation of an embodiment of the invention that provides multiple chambers for a single degree of freedom connected by a single conduit;
FIG. 7 is a schematic representation of an embodiment of the invention that provides multiple chambers for a single degree of freedom connected by multiple conduits;
FIG. 8A is a detailed view of an embodiment of the invention that includes a bellows type fluid displacer with the fluid located inside the bellows;
FIG. 8B is a detailed view of an embodiment of the invention that includes a piston type fluid displacer;
FIG. 9 is a detailed view of an embodiment of the invention that includes a piston type fluid displacer with a rolling seal;
FIG. 10 illustrates an embodiment of the invention that includes one chamber associated with a single degree of freedom of each sidestick;
FIG. 11 is a side view of a coupling assembly that includes one chamber with a piston type fluid displacer connected to a single degree of freedom for each sidestick according to an embodiment of the invention.